Etymology: < ancient Greek -ωνυμον, neuter singular combining form (in e.g. ὁμώνυμον homonym n., συνώνυμον synonym n.) of ancient Greek (Doric and Aeolic) ὀνύματ- , ὄνυμα name, word (ancient Greek (Attic) ὄνομα : see onomato- comb. form). Compare French -onyme (native formations in which are found from the early 19th cent.), German -onym.Combined with first elements ultimately of Greek origin. Earliest attested in synonym n., the proximate source of which is Latin (compare homonym n.). The proximate source of several other early formations is French (compare pseudonym n.). -onym occurs in a large number of formations from the late 19th and early 20th cent., a number of which are native formations in English, as acronym n., caconym n., mononym n., etc.
This is a new entry (OED Third Edition, June 2004; most recently modified version published online December 2018).